The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services from geosynchronous orbit. Payload systems for such spacecraft may include high power microwave radio frequency (RF) components such as travelling wave tube amplifiers (TWTA's) interconnected with waveguides. The payload may include a number of channels or paths in order to provide system redundancy or other functionalities that require switching. A substantial number of waveguide switches are necessary to enable redundant components to be switched in for components that have failed and to facilitate switching between alternate channels.
Flight qualified waveguide switches with extensive flight heritage include, four port, two channel switches (“C” switches, or C-switches) as illustrated in FIG. 1A through FIG. 1D, and, four port, three channel switches (“R” switches, or R-switches) as illustrated in FIG. 2A through FIG. 2F. Cracknell, U.S. Pat. No. 4,761,622, for example describes a C-switch (referred to therein as an “S” switch) and an R-switch of a known configuration.
A better understanding of a typical mechanical design of a C-switch may be obtained by referring to FIG. 1A which is a transverse section through stator 130 and rotor 110 of switch 100, and FIG. 1B, which is a longitudinal section view along line “b-b” through rotor 110 and bearings 120. Switch 100 includes rotor 110, which may generally be cylindrical in form, and which is arranged to rotate on bearings 120 in stator 130. Four waveguide channels 140, 150, 160, and 170 are located within stator 130 and provide passages along which microwave energy may be conveyed. Each of the waveguide channels 140, 150, 160, and 170 have an interior termination at a respective internal port A, B, C and D, adjacent to the rotor 110. Each of the waveguide channels 140, 150, 160 and 170 may be communicatively coupled via an exterior termination to respective external ports 101, 102, 103 and 104, illustrated in FIG. 1C. Ports A, B, C, and D may lie in a common plane and be arranged at 90 degree intervals around rotor 110. Rotor 110 includes two curved passages 180 and 190 located which are arranged such that their openings at the rotor circumference are spaced at 90 degree intervals. In the orientation shown in FIG. 1A, internal ports A and B are interconnected, as are internal ports C and D. Correspondingly, external ports 101 and 102 are interconnected, as are external ports 103 and 104. It will be appreciated, however, that if rotor 110 is rotated through 90 degrees in a clockwise or counter clockwise direction, the configuration of FIG. 1D will result, wherein external ports 101 and 104 are interconnected, as are external ports 102 and 103. Thus, as a result, energy transmitted into port 101 may be switched into either one of port 102 or port 104, depending on the orientation of rotor 110.
It will be appreciated that an identical connection arrangement results from rotating rotor 110 through 180 degrees in either the clockwise or counter clockwise direction. Thus, a C-switch is said to have 2 possible positions notwithstanding that rotor 110 may assume any one of 4 valid mechanical angular positions.
A better understanding of typical mechanical design of an R-switch may be obtained by referring to FIG. 2A, which is a transverse section through stator 230 and rotor 210 of switch 200, and FIG. 2B, which is a longitudinal section through rotor 210. An R-switch may be similar to the C-switch described above inasmuch as it includes two curved passages 280 and 290 within rotor 210. In addition, rotor 210 includes a further passage 285, which is straight and is arranged between curved passages 280 and 290, along a diameter of rotor 210.
The illustrated R-switch configuration permits a larger variety of interconnections to be made between four waveguide channels 240, 250, 260 and 270 located within stator 230, and having internal ports A, B, C and D respectively, than is possible with the C-switch illustrated in FIG. 1A through 1D. In the position illustrated in FIG. 2A, which corresponds to the configuration illustrated schematically in FIG. 2C, ports B and D only are interconnected. If, however, rotor 210 is rotated through 45 degrees clockwise from the position shown, then internal ports A and B are interconnected, and internal ports C and D are interconnected, by the curved passages 280 and 290 respectively, resulting in the configuration illustrated schematically in FIG. 2D. Similarly, if rotor 210 is rotated through 45 degrees counter clockwise from the position illustrated in FIG. 2A, then internal ports B and C are interconnected, and internal ports A and D are interconnected, resulting in the configuration illustrated schematically in FIG. 2E. Finally, if rotor 210 is rotated through 90 degrees, either clockwise or counter clockwise, from the position illustrated in FIG. 2A, then only ports A and C are interconnected, resulting in the configuration illustrated schematically in FIG. 2F.
Although C-switches and R-switches as described above are highly reliable and commonly used for space applications, they do not provide the flexibility required for some applications. For example, it may be observed that neither a C-switch nor an R-switch permits simultaneous connection of ports 101 with 103, and ports 102 with 104. This limitation can be avoided by a four port, four channel switch (“T switch” or T-switch), as illustrated schematically in FIG. 3A through FIG. 3C.
Satisfactory hardware solutions for the T-switch configuration illustrated schematically in FIG. 3A through FIG. 3C have eluded the industry, at least for applications demanding a waveguide interface suitable for high RF power applications. Proposed solutions described in U.S. Pat. Nos. 4,201,963, 6,201,906, and 6,489,858, for example, have not been adapted for space use because the solutions are mechanically complex, and pose reliability issues.
Thus, an improved approach to providing T-switch functionality is desired that avoids these shortcomings.